At least with JHP, they will be some deformation/expansion or a chance of it.
9mm FMJ will always be .355 diameter, nothing more. And a very good chance of exiting your target and hitting something you didn't want to hit.

If FMJ had any advantage, there wouldn't be close to 3/4 of a million LEO's in this country carrying JHP to work everyday.
Do you know of any departments or agencies that mandate that only FMJ be carried ?

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U. S. Army Veteran